Morphophysiological and Nutritional Responses of West Indian Gherkin Cultivars Under Salt Stress and Exogenous Carnitine Application

Water salinization severely limits agriculture in semiarid regions. This study evaluated the efficacy of exogenous carnitine (CAR) application in mitigating salt stress in two gherkin cultivars (Cucumis anguria L.), ‘Liso Gibão’ and ‘Do Norte’. The experiment used a randomized block design (3 × 3 factorial), combining three electrical conductivity levels of irrigation water (ECiw: 0.5, 2.5, and 4.5 dS m−1) and three foliar carnitine concentrations (0.0, 0.5, and 1.0 mM). The results indicated that increasing ECiw to 4.5 dS m−1 caused drastic reductions in growth, production, and photosynthetic efficiency, resulting in a 54.87% decrease in the number of fruits, due to toxic accumulation of Na+ and Cl−. However, carnitine supplementation (optimally at 0.5 mM) attenuated such damage, promoting significant increases in biomass (up to 55.43% for total dry mass), fruit number (by 23.37%), and gas exchange rates. The CAR application was associated with reduced Na+ accumulation (reducing leaf Na+ by 40.23% under moderate stress) and improved K+ and Ca2+ homeostasis. The cultivar ‘Do Norte’ showed higher carnitine-mediated tolerance, outperforming ‘Liso Gibão’. Carnitine acts as an effective biostimulant, with its application associated with improved ionic balance and gas exchange, supporting gherkin production under saline conditions.